Is Higher Current Necessary? Low-Current-Enhanced Electrocatalytic Ozonation through Synergistic Surface •OH Generation and Mass Transfer.

Abstract

This study challenges the conventional "higher current, better performance" paradigm in electrocatalytic ozonation (ECO) by demonstrating that reduced current operation simultaneously enhances pollutant removal, surface radical generation, and mass transfer through interface-dominated catalysis. Two systems using a TiO₂ nanoflower (TiO_2-NF)-modified porous anode coupled with graphite-loaded (GT-ECO) or pristine (PT-ECO) titanium mesh cathodes revealed fundamentally different reaction pathways. GT-ECO achieved complete <i>p</i>-CBA removal at 50 mA─4-fold lower than PT-ECO at 200 mA─through synergistic electrode functions: the TiO_2-NF anode enabled H₂O₂-independent O₃ activation, generating surface-localized •OH, while the GT cathode maintained elevated potentials for selective O₃ electroreduction without H₂ evolution. <i>In</i> <i>situ</i> electrochemical confocal fluorescence microscopy provided the first direct visualization of electric field-dependent surface •OH generation at the TiO_2-NF anode, confirming potential-regulated interfacial catalysis as the governing mechanism. Reduced current paradoxically enhances O₃ mass transfer of the O₃ at the porous anode through interfacial renewal, liquid film thinning, and bubble refinement. This anode-focused approach fundamentally departs from conventional cathode-driven H₂O₂-mediated strategies, enabling remarkable energy efficiency with operational safety and environmental robustness. These results emphasized the synergistic enhancement between surface catalysis and mass transfer and offered a new theoretical perspective on interfacial regulation in low-current ECO processes.